From 58398c3059f23afb247b9cd217fe79ee118ad4f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Thu, 30 Dec 2010 12:18:39 +0100
Subject: [PATCH] Function for computing inverse matrix.

---
 src/Math/Matrix.h            | 16 ++++++++++++++++
 src/Math/Test/MatrixTest.cpp | 21 +++++++++++++++++++++
 src/Math/Test/MatrixTest.h   |  1 +
 3 files changed, 38 insertions(+)

diff --git a/src/Math/Matrix.h b/src/Math/Matrix.h
index 7b0c596a6..45c2671a9 100644
--- a/src/Math/Matrix.h
+++ b/src/Math/Matrix.h
@@ -172,6 +172,22 @@ template<class T, size_t size> class Matrix {
             return out;
         }
 
+        /**
+         * @brief Inverse matrix
+         */
+        Matrix<T, size> inverse() const {
+            Matrix<T, size> out(false);
+
+            T _determinant = determinant();
+
+            for(size_t row = 0; row != size; ++row) {
+                for(size_t col = 0; col != size; ++col)
+                    out.set(row, col, (((row+col) & 1) ? -1 : 1)*ij(col, row).determinant()/_determinant);
+            }
+
+            return out;
+        }
+
     private:
         T _data[size*size];
 };
diff --git a/src/Math/Test/MatrixTest.cpp b/src/Math/Test/MatrixTest.cpp
index 5522df25d..c21af5fae 100644
--- a/src/Math/Test/MatrixTest.cpp
+++ b/src/Math/Test/MatrixTest.cpp
@@ -203,4 +203,25 @@ void MatrixTest::determinant() {
     QVERIFY(d == -2);
 }
 
+void MatrixTest::inverse() {
+    float m[] = {
+        3, 5, 8, 4,
+        4, 4, 7, 3,
+        7, -1, 8, 0,
+        9, 4, 5, 9
+    };
+
+    float inverse[] = {
+        -60/103.0f,      71/103.0f,     -4/103.0f,      3/103.0f,
+        -66/103.0f,     109/103.0f,     -25/103.0f,     -7/103.0f,
+        177/412.0f,     -97/206.0f,     53/412.0f,      -7/206.0f,
+        259/412.0f,     -185/206.0f,    31/412.0f,      27/206.0f
+    };
+
+    Matrix4 _inverse = Matrix4(m).inverse();
+
+    QVERIFY(_inverse == Matrix4(inverse));
+    QVERIFY(_inverse*Matrix4(m) == Matrix4());
+}
+
 }}}
diff --git a/src/Math/Test/MatrixTest.h b/src/Math/Test/MatrixTest.h
index 3b190881d..19db2f92d 100644
--- a/src/Math/Test/MatrixTest.h
+++ b/src/Math/Test/MatrixTest.h
@@ -33,6 +33,7 @@ class MatrixTest: public QObject {
         void transposed();
         void ij();
         void determinant();
+        void inverse();
 };
 
 }}}